Astrophysics > Astrophysics of Galaxies

Title:
MOND impact on and of the recently updated mass-discrepancy-acceleration relation

Abstract: McGaugh et al. (2016) have used their extensive SPARC sample to update the
well-known mass-discrepancy-acceleration relation (MDAR), which is one of the
major predicted "MOND laws". This is not a newly discovered relation. Rather,
it improves on the many previous studies of it, with more and better data. Like
its precedents, it bears crucial ramifications for the observed dynamical
anomalies in disc galaxies, and, in particular, on their resolution by the MOND
paradigm. Their result, indeed, constitute a triumph for MOND. However, unlike
previous analyses of the MDAR, McGaugh et al. have chosen to obfuscate the MOND
roots of their analysis, and its connection with, and implications for, this
paradigm. For example, the fitting formula they use, seemingly as a result of
some unexplained inspiration, follows in its salient properties from the basic
tenets of MOND, and has already been used in the past in several MOND analyses.
No other possible origin for such a function is known. Given that this formula
had already been shown to reproduce correctly the observed rotation curves from
the baryon distribution (as a MOND effect), it must have been clear, a priory,
that it should describe correctly the MDAR, which is but a summary of rotation
curves. The present paper corrects these oversights -- bringing to light the
deep connections with MOND, suppressed by McGaugh et al. It also gives due
credit to previous works, and discusses some new, important, but less known,
aspects of this MOND relation. (Substantially abridged.)

Comments:

4 pages. Added a discussion, enlarged the discussion of the MOND interpolation function, corrected typos, and added various references